Air induction system having inlet valve

ABSTRACT

An air induction system ( 10 ) for use with an internal combustion engine (E) including an intake is disclosed. The system ( 10 ) includes a supercharger ( 12 ) and a valve assembly. The valve assembly comprises a valve ( 14 ) and a valve control mechanism ( 16 ). The supercharger ( 12 ) receives air through a supply opening ( 18 ), pressurizes it, and discharges it through an exhaust opening ( 20 ). The valve ( 14 ) is in communication with the supply opening ( 18 ) to control air supply thereto. The control mechanism ( 16 ) is coupled to the valve ( 14 ) and causes it to vary the air supply to the opening ( 18 ) in response to air pressure conditions downstream from the supercharger ( 12 ). In one embodiment, the control mechanism ( 16 ) varies the air supply responsive to air pressure in the intake in order to both throttle the supercharger ( 12 ) as well as substantially eliminate undesirable surge conditions therein. In another embodiment, the control mechanism ( 118 ) varies the air supply responsive to air pressure in the inlet ( 110 ) of a turbocharger ( 106 ) to provide supercharged air thereto at a substantially constant pressure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Provisional Application Ser.No.60/301,264, filed Jun. 27, 2001, entitled AIR INDUCTION SYSTEM HAVINGINLET VALVE, which is hereby incorporated by reference herein.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates generally to air induction systems forproviding increased airflow to the intake of an engine. Moreparticularly, the present invention concerns a supercharger systemhaving an inlet valve that varies the supply of air to the superchargerin response to air pressure conditions downstream from the supercharger.The downstream air pressure conditions can vary depending on theapplication and could include for example pressure conditions in theengine intake or pressure conditions in the inlet to a downstreamturbocharger.

2. Discussion of Prior Art

Centrifugal superchargers that increase air flow to an engine (therebyincreasing the power generated thereby) are known in the art andtypically utilize a compressor powered by the engine's crankshaft tosupply pressurized air, or “boost,” to the engine. Known prior artcentrifugal superchargers, however, are problematic and have severallimitations. For example, conventional centrifugal superchargers have asomewhat linear boost response curve, therefore, if optimal boost isprovided at higher engine rpms, the boost provided at lower engine rpmsis significantly less than optimal. Conversely, if the typicalcentrifugal supercharger is set up to provide optimal boost at lowerengine rpms, it will provide more boost than the engine can handle athigher engine rpms.

Known centrifugal superchargers are also problematic in that they sufferfrom undesirable surge conditions that are counterproductive to theoperation of both the supercharger and the engine. For example, when adownstream restriction occurs, such as the closing of the enginethrottle, the large pressure loads created can destroy the internalparts of the supercharger. Some prior art superchargers utilize a bypassvalve that dumps the load into a recirculating line during these surgeconditions; however, this bypass valve solution is problematic in thatan undesirable pressure spike still occurs and the resulting pressurefluctuations can cause the mass flow meter to feed too much fuel intothe engine.

Turbochargers, similar to superchargers, increase air flow to an engine;however, turbochargers utilize a compressor powered by the exhaustoutput by the engine. Known turbochargers also suffer from low-end boostproblems, similar to those described above. Some prior art turbochargersutilize a supercharger upstream from Add the turbocharger, and poweredby the engine's crankshaft, to supplement its low-end boost. Thesesupercharged turbochargers, however, are problematic and have severallimitations. For example, known supercharged turbochargers have anundesirable variance in the pressure supplied to the inlet of theturbocharger. That is, they are only supercharged at lower engine rpmsand not operable to be supercharged at higher engine rpms. This isparticularly problematic in high altitude applications whereinturbochargers typically do not supply sufficient boost for the desiredengine power output. For example, diesel powered trucks frequently useturbochargers to boost engine power and these trucks are commonly usedto transport heavy loads through high altitude conditions wherein theboost provided by the turbocharger at higher engine rpms is insufficientto desirably power the engine. Additionally, high altitude conditionslower volumetric efficiency and increase exhaust emissions.

SUMMARY OF INVENTION

The present invention provides an improved air induction system thatdoes not suffer from the problems and limitations of prior art systemsset forth above. The inventive system provides an inlet valve thatvaries the supply of air to the supercharger in response to air pressureconditions downstream from the supercharger. The valve can be used toboth throttle the supercharger as well as substantially eliminateundesirable surge conditions therein by selecting pressure conditions inthe intake to the engine as the controlling downstream pressureconditions. The inventive system can also be used to providesupercharged air at a substantially constant pressure to a turbochargerby selecting pressure conditions in the inlet to the turbocharger as thecontrolling downstream pressure conditions.

A first aspect of the air induction system of the present inventionconcerns a system for inducing airflow into the intake of an internalcombustion engine including and broadly includes a centrifugalsupercharger presenting an air supply opening and a spaced pressurizedair exhaust opening and being operable to pressurize air between thesupply and exhaust openings, and a valve in communication with thesupply opening to control air supply thereto.

A second aspect of the air induction system of the present inventionconcerns a valve assembly to be used in an air induction system thatinduces airflow into the intake of an internal combustion engine,wherein the induction system includes a compressor presenting an airsupply opening and a spaced pressurized air exhaust openingcommunicating with the engine intake. The valve assembly broadlyincludes a valve fluidly connectable to the supply opening to controlair supply thereto, and a valve control mechanism including an airpressure sensor adapted to sense air pressure downstream from the airexhaust opening. The valve control mechanism is operable to cause thevalve to vary the air supply depending on the air pressure sensed.

Another aspect of the air induction system of the present inventionconcerns an air induction system in a powered vehicle including anengine. The induction system broadly includes a turbocharger operable topressurize air and deliver it to the engine and including an inletoperable to receive air. The induction system further includes asupercharger in communication with the inlet and being operable topressurize air and deliver it to the inlet, wherein the superchargerincludes an air supply opening operable to receive air. In addition, theinduction system includes a valve in communication with the supplyopening and being operable to vary air supply thereto so that airpressure of the pressurized air delivered to the inlet remainssubstantially constant.

Other aspects and advantages of the present invention will be apparentfrom the following detailed description of the preferred embodiments andthe accompanying drawing figures.

BRIEF DESCRIPTION OF DRAWINGS

Preferred embodiments of the invention are described in detail belowwith reference to the attached drawing figures, wherein:

FIG. 1 is a plan view of an air induction system constructed inaccordance with a preferred embodiment of the present invention andshown in combination with an internal combustion engine (illustrated ina fragmentary and partially schematic view);

FIG. 2 is an enlarged longitudinal vertical sectional view of the inletvalve assembly of the induction system illustrated in FIG. 1 with aportion of the control mechanism broken away and illustrating the valvein the open position;

FIG. 3 is an enlarged longitudinal vertical sectional view of the inletvalve assembly with a portion of the control mechanism broken away andillustrating the valve in the over-boost induced closed position;

FIG. 4 is an enlarged longitudinal vertical sectional view of the inletvalve assembly with a portion of the control mechanism broken away andillustrating the valve in the surge-induced closed position;

FIG. 5 is a side elevational view of an air induction system constructedin accordance with an alternative embodiment of the present inventionand shown in combination with an internal combustion engine in a truck;and

FIG. 6 is an enlarged plan view of the system illustrated in FIG. 5 andshown in combination with the engine (illustrated in a fragmentary andpartially schematic view).

DETAILED DESCRIPTION

Turning initially to FIG. 1, the air induction system 10 selected forillustration is shown in use with an internal combustion engine E of avehicle such as a boat or automobile. Although the illustrated engine Ehas eight cylinders, the principles of the present invention are equallyapplicable to various other types of engines. It is noted, however, thatthe air induction system 10 is preferably driven directly by the engineE, for example, the system 10 is drivingly coupled to the crankshaft ofthe engine E by a belt drive. Moreover, the system 10 is connected tothe engine intake, including an intake plenum box B and an intakemanifold M, by a conduit C, such that pressurized air generated by thesystem 10 is directed to the intake. In addition, an intercooler I ispreferably in air communication with the conduit C to cool thepressurized air prior to it entering the intake. The principles of thepresent invention are not limited to the illustrated applications, butrather the inventive system 10 may be utilized in any application inwhich a highly pressurized, controlled air stream is desired (e.g.,various other types of reciprocating engines, etc.). The illustrated airinduction system 10 broadly includes a supercharger 12 in communicationwith a valve assembly. The valve assembly includes a valve 14 and avalve control mechanism 16.

The illustrated supercharger 12 receives air through an air supplyopening 18, pressurizes the air in a compressor, and discharges thepressurized air through an air exhaust opening 20. The illustratedsupercharger 12 is preferably a centrifugal supercharger including arotatable impeller and a step-up drive mechanism drivingly coupling theimpeller to the engine E. However, the supercharger could be variouslyconfigured utilizing any suitable alternative design. Representativesuperchargers are disclosed in the following filed applications for U.S.Letters Patents (assigned of record to the assignee of the presentapplication): Ser. No. 09/669,018, entitled GEAR DRIVEN SUPERCHARGERHAVING NOISE REDUCING IMPELLER SHAFT; Ser. No. 09/668,223, entitledCENTRIFUGAL SUPERCHARGER HAVING LUBRICATING SLINGER; and Serial No.09/706,007, entitled VELOCITY VARIANCE REDUCING MULTIPLE BEARINGARRANGEMENT FOR IMPELLER SHAFT OF CENTRIFUGAL SUPERCHARGER, which areall hereby incorporated by reference herein as is necessary for a fulland complete understanding of the present invention. Most preferably,one or more of the supercharger designs disclosed in the foregoingapplications will be utilized, as it is believed that they provide asupercharger capable of withstanding the additional operational loadsexperienced when an inlet valve is incorporated into the inductionsystem. In particular, these supercharger designs provide long-lasting,durable bearing arrangements and a device that is unlikely tocatastrophically fail due to the necessary higher operational speeds.

Air is supplied to the supercharger 12 by an inlet comprising an airfilter 22, the valve 14, and the air supply opening 18 (see FIG. 1). Airis discharged to the engine E through an outlet comprising the airexhaust opening 20, the conduit C, the intercooler 1, the intake box B,and the intake manifold M. Although not illustrated, the inlet mayalternatively communicate with a forwardly open conduit (not shown) thatextends toward the front of the powered vehicle, such that air flow tothe supercharger 12 is facilitated when the vehicle is moving in aforward direction. The valve 14 is in air communication with the airsupply opening 18 and positioned upstream therefrom. The valve 14controls the air supply to the supply opening 18, which in turn controlsthe supply of air discharged to the engine E.

In particular, the valve 14 includes a housing 24 and a valve body 26(see FIG. 2). The housing 24 is generally cylindrically shaped andincludes open ports 28,30 on each opposing end. The filter 22 adjoinsone end of the housing 24 so that port 28 is in air communication withthe filter 22. The opposing end of the housing 24 adjoins the air supplyopening 18 of the supercharger 12 so that port 30 is in aircommunication with the air supply opening 18. For purposes that willsubsequently be described, the housing 24 further includes a radiallyenlarged section 32 defining a diameter that is greater than thediameter of each of the ports 28, 30. In this manner, two pairs ofshoulders 34, 36 and 38, 40 are formed on the inside surface of thehousing 24. A pair of shoulders is adjacent each of the correspondingports 28, 30. The housing 24 also includes a centrally located axialshaft 42 fixed to the housing 24 by a pair of spokes 44, 46. It will beappreciated that each of the spokes 44, 46 are configured so that anyobstruction of air flow through the housing 24 caused thereby isminimal, although alternative spoke configurations could be utilized(e.g., horizontal spokes, multiple spokes adjacent each port, etc.).

The valve body 26 is slidably mounted on the shaft 42 within the section32 of the housing 24. The valve body 26 is generally disc shaped havingcentral apertures corresponding to the circumference of the shaft 42 toprovide sliding of the valve body 26 relative to the shaft 42. The valvebody 26 is generally concentric with the housing 24. The valve body 26defines a body cross-sectional area that is greater than the innercross-sectional area of each of the ports 28, 30 but less than the innercross-sectional area of the section 32. In this manner, the valve body26 is shiftable linearly along the shaft 42 between an open position asillustrated in FIG. 2, wherein the valve body 26 is generally coplanarwith the center bulge section 32 so that air supply to the supplyopening 18 (designated by arrows in FIG. 2) is substantiallyunrestricted by the valve body 26, and a closed position as illustratedin either of FIGS. 3 or 4, wherein the valve body 26 is adjacent eitherpair of shoulders 34, 36 (FIG. 4) or 38, 40 (FIG. 3) so that air supplyto the supply opening 18 is substantially restricted relative to thevalve body 26 being in the open position. It will be appreciated that asthe valve body 26 moves toward a respective pair of shoulders 34, 36 or38, 40, the air supply to the supply opening 18 will becomeprogressively more restricted. Although the illustrated valve 14 is notshown with the valve body 26 physically engaging the paired shoulders34, 36 or 38, 40 (nor is it imperative to the present invention), it ispossible in application that the shoulders 34, 36 or 38, 40 actuallyfunction as a valve seat and physically engage the valve body 26 so thatthe air supply to the supply opening 18 is virtually shut off. Forpurposes that will subsequently be described, the valve body 26 definesa generally sealed internal cavity. It will be appreciated that giventhe importance of the valve body 26 being able to freely slide relativeto the shaft 42, it may not be possible to completely seal the internalcavity relative to the central apertures.

The valve could utilize various alternative designs, configurations,constructions, materials, etc., so long as the valve is operable tocontrol air supply to the supercharger. Any type of suitableflow-control valve could be used utilizing many different housing, body,and seat configurations, for example, a square shaped housing, a simplebutterfly valve, etc. However, it is preferred that the selected valvebe operable to regulate or control air flow rather than merely being agate that is either fully open or fully closed.

The valve control mechanism 16 senses air pressure downstream from thesupercharger 12. The valve control mechanism causes the valve 14 to varythe air supply to the supply opening 18 depending upon the downstreampressure conditions sensed. In particular, the control mechanism 16includes a flexible diaphragm 48, an atmosphere reference aperture 50,and an intake reference line 52. The flexible diaphragm 48 is fixed atboth ends within the internal cavity of the valve body 26, generally atthe center of the valve body 26, so that the diaphragm 48 and the valvebody 26 cooperate to define two pneumatically isolated, collapsiblechambers 54, 56. The diaphragm 48 includes a center aperture to allowinsertion of the shaft 42 during assembly, however, once assembled thediaphragm 48 is fixed to the shaft 42 and sealed thereto by a sealingring 58. The chamber 54 communicates with the atmospheric pressure inthe housing 24 by the atmosphere reference aperture 50 so that pressurewithin the chamber 54 is generally the same as the atmospheric pressurewithin the housing 24.

The intake reference line 52 is connected at one end to the intakemanifold M of the engine E with the other end venting into the chamber56. In particular, an innervalve pathway 52 a is formed through an upperportion of the axial center of the spoke 46 and through a portion of theaxial center of the shaft 42 that extends between the spoke 46 and thechamber 56. The pathway 52 a extends radially through the shaft 42 sothat the pathway 52 a opens into the chamber 56 (see, e.g., FIG. 2). Itwill be appreciated that the pathway 52 a could be formed in a number ofdifferent methods (e.g., drilling, molding during formation of therelevant parts, etc.). The inner-valve pathway 52 a connects to anouter-valve pathway 52 b to complete the reference line 52. Theouter-valve pathway is comprised of tubing threadably connected at oneend to the exterior of the housing 24 and coupled to the intake manifoldM at the other end. In this manner, air pressure in the intake manifoldM is communicated through the reference line 52 to the chamber 56 sothat pressure within the chamber 56 is generally the same as thepressure within the intake manifold M.

The valve control mechanism 16 causes the valve 14 to vary the airsupply to the supply opening 18 depending upon air pressure in theintake manifold M (as communicated to the chamber 56 by the referenceline 52) relative to a reference pressure. The reference pressure is theatmospheric pressure in the housing 24 as communicated to the chamber 54by the aperture 50. In particular, the control mechanism 16 causes thevalve body 26 to shift out of the open position toward the closedposition illustrated in FIG. 4 (i.e., toward the paired shoulders 34,36) thereby progressively restricting the air supply to the supplyopening 18 when the downstream pressure condition is a surge condition.The surge condition occurs when the air pressure in the intake manifoldM (and thus the air pressure in the chamber 56) is less than thereference atmospheric pressure in the housing 24 (and thus the airpressure in the chamber 54). The pressure differential caused by thesurge condition collapses the chamber 56 while the chamber 54simultaneously expands. Because the diaphragm 48 is fixed to the shaft42, the expansion of the chamber 54 causes the valve body 26 to shifttoward the paired shoulders 34, 36.

The control mechanism 16 causes the valve body 26 to shift out of theopen position toward the closed position illustrated in FIG. 3 (i.e.,toward the paired shoulders 38, 40) thereby progressively restrictingthe air supply to the supply opening 18 when the downstream pressurecondition is an over-boost condition. The over-boost condition occurswhen the air pressure in the intake manifold M (and thus the airpressure in the chamber 56) is greater than the reference atmosphericpressure in the housing 24 (and thus the air pressure in the chamber54). The pressure differential caused by the over-boost conditionexpands the chamber 56 while the chamber 54 simultaneously collapses.Because the diaphragm 48 is fixed to the shaft 42, the expansion of thechamber 56 causes the valve body 26 to shift toward the paired shoulders38, 40.

The valve body 26 is yieldably biased into the open position by a pairof springs 60, 62. The springs 60, 62 are slidably mounted on the shaft42, with each spring 60, 62 being positioned in a respective one of thechambers 54, 56. The springs 60, 62 freely float along the shaft 42. Inaddition to biasing the valve body 26 into the open position, thesprings 60, 62 also cooperate with the pressure differential between thechambers 54, 56 to determine when the valve 14 opens and closes. Thatis, the pressure differential in the chambers 54, 56 must overcome thespring force in the corresponding spring 60, 62 in order to collapse andexpand the chambers and thereby shift the valve body 26 to a closedposition. In this manner, the valve assembly can be tailored to aspecific application by selecting a spring, or a pair of springs, havinga particular spring force in order to set the conditions in which thevalve opens and closes.

The valve control mechanism could utilize various alternative designs,configurations, constructions, etc., so long as the control mechanism isoperable to cause the valve to vary the air supply to the supercharger.For example, the valve could be electronically or mechanicallycontrolled. In addition, it is within the ambit of the present inventionto utilize a valve control mechanism that does not automatically sensethe valve-control conditions, for example, the valve could be remotelycontrolled by the vehicle operator selecting an open or close functiondepending on the operator's needs or desires.

In operation, air is drawn through the inlet into the supercharger 12where it is pressurized and delivered to the engine E through theoutlet. The step-up drive powers the supercharger 12 off of the engine Eso that the supercharger 12 provides the desired boost at low-end enginespeeds (e.g., 10 psi at 2500 rpm). As the engine speed increases, thevalve control mechanism 16 causes the valve 14 to shift out of the openposition thereby controlling the air supply to the supercharger 12 sothat the supercharger 12 provides the desired boost withoutover-boosting at high-end engine speeds (e.g., 10 psi at 6000 rpm).Should a downstream restriction occur (e.g., the engine throttlecloses), the valve control mechanism 16 causes the valve 14 to closethereby controlling the air supply to the supercharger 12 so thatundesirable pressure spikes are prevented.

The inventive air induction system of the present invention could beconfigured for many different applications in which a controlled streamof pressurized air is desired. For example, the downstream pressureconditions that control the valve operation could be varied depending onthe desired application. One such alternative embodiment is the airinduction system 100 illustrated in FIGS. 5 and 6. Turning initially toFIG. 5, the air induction system 100 selected for illustration is shownin use with an internal combustion engine E of a truck T. Although thesystem 100 could be used in any internal combustion engine, it is mostpreferably a diesel engine (e.g., the type typically used by theover-the-road trucking industry, road working equipment, etc.). The airinduction system 100 broadly includes a supercharger 102 incommunication with a valve assembly 104, located upstream from thesupercharger 102, and a turbocharger 106, located downstream from thesupercharger 102.

The illustrated supercharger 102 is a centrifugal supercharger poweredby the crankshaft of the engine E and is substantially similar to thesupercharger 12 previously described, however, the air induction system100 could utilize any suitable supercharger (e.g., Roots-type,screw-type, etc.). The illustrated supercharger 102 receives air throughan air supply opening 108, pressurizes the air, and outputs thepressurized air through an air exhaust opening.

The illustrated turbocharger 106 includes an inlet 110 for receivingpressurized air from the supercharger 102 through conduit 112. Althoughnot illustrated, an intercooler (not shown) could be included betweenthe exhaust opening of the supercharger 102 and the inlet 110 of theturbocharger 106. The turbocharger 106 further pressurizes the airreceived in inlet 110 and delivers it to the engine E through outlet114. The illustrated turbocharger 106 is a conventional turbochargerpowered by the exhaust from the engine E and in this regard is in powercommunication with the exhaust manifold (not shown) of the engine E. Theturbocharger could have many different configurations readilyappreciated by those skilled in the art.

The valve assembly 104 is in communication with the air supply opening108 of the supercharger 102 to vary air supply thereto. The valveassembly 104 is similar to the previously discussed valve assembly(illustrated in FIGS. 1-4) and includes a valve 116 and a valve controlmechanism 118. However, the valve control mechanism 118 is coupledbetween the valve 116 and the inlet 110 of the turbocharger 106 ratherthan the intake manifold of the engine E. In this manner, the valvecontrol mechanism 118 senses pressure conditions in the inlet 110 of theturbocharger 106. The valve control mechanism 118 causes the valve 116to progressively restrict the air supply to the supply opening 108 ofthe supercharger 102 depending upon pressure conditions in the inlet 110of the turbocharger 106 relative to the atmospheric pressure in thevalve 116. The valve 116 controls the air supply to the supply opening108 of the supercharger 102 so that the air pressure in the inlet 110 ofthe turbocharger 106 remains substantially constant.

The inventive air induction system 100 compensates for changes inatmospheric pressure occasioned by changes in altitude (e.g., the inletof the turbocharger receives pressurized air at a substantially constantpressure regardless of atmospheric pressure). In addition to stabilizingthe boost in power output by the engine, it is believed using theinventive air induction system to supercharge a turbocharger alsoincreases fuel efficiency and reduces emissions. Supercharging aturbocharger with the inventive system also provides the conventionaladvantage of providing boost to the turbocharger at low-end enginespeeds.

The preferred forms of the invention described above are to be used asillustration only, and should not be utilized in a limiting sense ininterpreting the scope of the present invention. Obvious modificationsto the exemplary embodiments, as hereinabove set forth, could be readilymade by those skilled in the art without departing from the spirit ofthe present invention.

The inventors hereby state their intent to rely on the Doctrine ofEquivalents to determine and assess the reasonably fair scope of thepresent invention as pertains to any apparatus not materially departingfrom but outside the literal scope of the invention as set forth in thefollowing claims.

What is claimed is:
 1. An air induction system for inducing airflow intothe intake of an internal combustion engine, the system comprising: acentrifugal supercharger presenting an air supply opening and a spacedpressurized air exhaust opening and being operable to pressurize airbetween the supply and exhaust openings; a valve in communication withthe supply opening to control air supply thereto; and a valve controlmechanism coupled to the valve to cause the valve to vary the air supplydepending upon a condition, said control mechanism being connectable tothe engine to cause the valve to vary the air supply depending upon airpressure in the intake, said control mechanism being operable to causethe valve to progressively restrict the air supply to the supply openingwhen said condition is a surge condition wherein air pressure in theintake is less than a reference pressure.
 2. The induction system asclaimed in claim 1, said supercharger including a rotatable impeller. 3.The induction system as claimed in claim 2, said supercharger includinga step-up drive mechanism for drivingly coupling the impeller to theengine.
 4. An air induction system for inducing airflow into the intakeof an internal combustion engine, the system comprising: a centrifugalsupercharger presenting an air supply opening and a spaced pressurizedair exhaust opening and being operable to pressurize air between thesupply and exhaust openings; a valve in communication with the supplyopening to control air supply thereto; and a valve control mechanismcoupled to the valve to cause the valve to vary the air supply dependingupon a condition, said control mechanism being connectable to the engineto cause the valve to vary the air supply depending upon air pressure inthe intake, said control mechanism being operable to cause the valve toprogressively restrict the air supply to the supply opening when saidcondition is an over-boost condition wherein air pressure in the intakeis greater than a reference pressure.
 5. The induction system as claimedin claim 4, said supercharger including a rotatable impeller.
 6. Theinduction system as claimed in claim 5, said supercharger including astep-up drive mechanism for drivingly coupling the impeller to theengine.
 7. An air induction system for inducing airflow into the intakeof an internal combustion engine, the system comprising: a centrifugalsupercharger presenting an air supply opening and a spaced pressurizedair exhaust opening and being operable to pressurize air between thesupply and exhaust openings; and a valve in communication with thesupply opening to control air supply thereto, said valve including avalve body shiftable into and out of an open position wherein the airsupply to the supply opening is substantially unrestricted by the valvebody.
 8. The induction system as claimed in claim 7; and a valve controlmechanism coupled to the valve to cause the valve to vary the air supplydepending upon a condition.
 9. The induction system as claimed in claim8, said control mechanism being connectable to the engine to cause thevalve to vary the air supply depending upon air pressure in the intake.10. The induction system as claimed in claim 7, said valve body beingyieldably biased into the open position.
 11. An air induction system forinducing airflow to the intake of an internal combustion engineincluding an intake, the system comprising: a centrifugal superchargerpresenting an air supply opening and a spaced pressurized air exhaustopening and being operable to pressurize air between the supply andexhaust openings; a valve in communication with the supply opening tocontrol air supply thereto; and a valve control mechanism coupled to thevalve to cause the valve to vary the air supply depending upon acondition, said control mechanism being connectable to the engine andbeing operable to cause the valve to progressively restrict the airsupply to the supply opening when said condition is either a surgecondition wherein air pressure in the intake is less than a referencepressure, or an over-boost condition wherein air pressure in the intakeis greater than a reference pressure.
 12. In a powered vehicle includingan engine, an improved air induction system comprising: a turbochargeroperable to pressurize air and deliver the pressurized air to the engineand including an inlet operable to receive air; a supercharger incommunication with said inlet and being operable to pressurize air anddeliver the pressurized air to said inlet, said supercharger includingan air supply opening operable to receive air; and a valve incommunication with the supply opening and being operable to vary airsupply thereto so that air pressure of the pressurized air delivered tothe inlet remains substantially constant.
 13. In the powered vehicle asclaimed in claim 12, and a valve control mechanism coupled between thevalve and the inlet and being operable to cause the valve toprogressively restrict the air supply to the supply opening dependingupon pressure conditions in the inlet relative to atmospheric pressure.14. In a powered vehicle including an internal combustion engine havingan intake, an improved air induction system comprising: a centrifugalsupercharger presenting an air supply opening and a spaced pressurizedair exhaust opening and being operable to pressurize air between thesupply and exhaust openings and deliver the pressurized air to theintake; a valve in communication with the supply opening to control airsupply thereto; and a valve control mechanism coupled to the valve tocause the valve to vary the air supply depending upon a condition, saidcontrol mechanism being connectable to the engine to causevalve-controlled variance in the air supply depending upon air pressurein the intake, said control mechanism being operable to cause the valveto progressively restrict the air supply to the supply opening when saidcondition is a surge condition wherein air pressure in the intake isless than a reference pressure.
 15. In the powered vehicle as claimed inclaim 14, said valve including a valve body shiftable into and out of anopen position wherein the air supply to the supply opening issubstantially unrestricted by the valve body.
 16. In the powered vehicleas claimed in claim 15, said valve body being yieldably biased into theopen position.
 17. In a powered vehicle including an internal combustionengine having an intake, an improved air induction system comprising: acentrifugal supercharger presenting an air supply opening and a spacedpressurized air exhaust opening and being operable to pressurize airbetween the supply and exhaust openings and deliver the pressurized airto the intake; a valve in communication with the supply opening tocontrol air supply thereto; and a valve control mechanism coupled to thevalve to cause the valve to vary the air supply depending upon acondition, said control mechanism being connectable to the engine tocause valve-controlled variance in the air supply depending upon airpressure in the intake, said control mechanism being operable to causethe valve to progressively restrict the air supply to the supply openingwhen said condition is an over-boost condition wherein air pressure inthe intake is greater than a reference pressure.
 18. In the poweredvehicle as claimed in claim 17, said valve including a valve bodyshiftable into and out of an open position wherein the air supply to thesupply opening is substantially unrestricted by the valve body.
 19. Inthe powered vehicle as claimed in claim 15, said valve body beingyieldably biased into the open position.
 20. In a powered vehicleincluding an engine, an improved air induction system comprising: aturbocharger operable to pressurize air and deliver the pressurized airto the engine and including an inlet operable to receive air; asupercharger in communication with said inlet and being operable topressurize air and deliver the pressurized air to said inlet, saidsupercharger including an air supply opening operable to receive air;and a valve in communication with the supply opening to control airsupply thereto.
 21. In a the powered vehicle as claimed in claim 20; anda valve control mechanism coupled between the valve and the inlet andbeing operable to cause the valve to progressively restrict the airsupply to the supply opening depending upon pressure conditions in theinlet relative to atmospheric pressure.